diff --git a/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java b/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java
index 960f4bec5eeb5..525dcc056eab1 100644
--- a/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java
+++ b/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java
@@ -83,7 +83,7 @@ public static <R extends Reader<?>> void registerReader(final byte ordinal, fina
 
         public static void registerClassAlias(final Class<?> classInstance, final Class<?> classGeneric) {
             if (WRITER_CUSTOM_CLASS_MAP.putIfAbsent(classInstance, classGeneric) != null) {
-                throw new IllegalArgumentException("Streamable custom class already registered [" + classInstance.getClass() + "]");
+                throw new IllegalArgumentException("Streamable custom class already registered [" + classInstance + "]");
             }
         }